Eiberweiser, Andreas and Nazet, Andreas and Hefter, Glenn and Buchner, Richard (2015) Ion Hydration and Association in Aqueous Potassium Phosphate Solutions. JOURNAL OF PHYSICAL CHEMISTRY B, 119 (16). pp. 5270-5281. ISSN 1520-6106,
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Ionic hydration and ion association in aqueous solutions of KH2PO4, K2HPO4, and K3PO4 at 25 degrees C up to high concentrations-have been investigated using dielectric relaxation spectroscopy (DRS). The three phosphate anions were found to be extensively: hydrated, with total hydration numbers at infinite dilution of similar to 11 (for H2PO4-, similar to 20 (HPO42-), and similar to 39 (PO43-). These values are indicative of the existence of a second hydration shell around HPO42- and especially PO43-. Two types of hydrating water molecules could be quantified: irrotationally bound (ib, H2O molecule essentially "frozen" on the DRS time Scale) and "slow" (loosely bound water molecules With identifiably slower dynamics than bulk water). For H2O4- over the entire concentration range and for HPO42- and PO43- at concentrations c less than or similar to 1 mol L-1, only "slow" H2O was detected; however, at higher concentrations of the latter two anions, an increasing fraction of ib water appears, making up, similar to 50% of the total hydration number Close to the saturation limit of K2HPO4. Contrary to common belief, all three salts showed significant ion pair formation, with standard association constants of the 1:1 species increasing in the order: KH2PO40(aq) < KHPO4-(aq) < KPO42-(aq). The main type of ion pair in solution shifted from solvent-shared ion pairs (SIPs) to double-solvent-separated ion pairs (2SIPs) in the same sequence.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | DIELECTRIC-RELAXATION SPECTROSCOPY; FOLGE CHEMISCHER RELAXATION; ELECTROLYTE-SOLUTIONS; MOLECULAR-DYNAMICS; WATER; SODIUM; PROTONATION; SCHALLABSORPTION; SCATTERING; ANIONS; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 22 Jul 2019 12:51 |
| Last Modified: | 22 Jul 2019 12:51 |
| URI: | https://pred.uni-regensburg.de/id/eprint/5626 |
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